Process for production of pressure sensitive recording medium



Aug. 18, 1964 PROCESS FOR A. KATCHALSKY ETAL 3,145,117 PRODUCTION OFPRESSURE SENSITIVE RECORDING MEDIUM Filed March 22. 1961 A/VO 4901/0452POL YOLEF/IV 0/1170! VED //V J01 I/E/Vi' 47' EL 51 4750 TEN/[47 019! J7' 065 ff/E IN VEN TOR.

United States Patent C) 3,145,117 PROCES FQR PRQDUCTTON F PRESdURESENSl'lll E REUURDlNG MEDIUM Aharon Katchalsky, lid Dulrnov Sh, TelAviv, Israel;

David Vofsi, Meonot Voifson 4, Yad Weizmann, Rehnvotlr, Israel; and SaulAlexander Gassner, 17 Kolrhavi St., Shkhunat Ephraim, Rehovoth, lisraelFiled Mar. 22, 19611, Ser. No. 97,444- i 4- Clairns. (Cl. 1l7--36.7)

It is an object of the present invention to provide a novel recordingmedium.

It is a further object of the present invention to provide a method forthe manufacture of such recording medium.

More particularly it is an object of the present invention to provide anovel recording medium which comprises a supporting sheet coated with anopaque coating, having a color differing from that of the surfacecoated, and being so constituted that the impact of mechanical forcerenders the coating translucent in the impacted area.

It is a further object of the present invention to provide such coatingwhich has a foamed structure, which is opaque and which is renderedtranslucent in the impacted area.

It is a further object of the present invention to pro vide a convenientmethod for the manufacture of such recording medium.

Other objects will appear hereinafter.

Hitherto scientific instruments of the recording type have been usedwith different recording means for recording the data obtained, varyingfrom recording said information in a legible script by means of an inkednib to rather complicated photographic and electrical methods.

The novel medium, according to the invention, comprises a sheet providedwith a coating of a color different from that of the surface coated,said coating being so constituted that the application of mechanicalforce, such as the impact of a typewriter key or stylus, results in alegible mark in the impacted area. Such mechanical force may be appliedby means of a pointed implement. On the other hand impact such as bymeans of a typewriter key, may be resorted to.

A recording medium according to the invention comprises in combination asupporting sheet, such as paper, cardboard, plastic sheeting or thelike, coated with an opaque layer of a polymeric substance as defined,having a foamed structure, admixed with a binder for enhancing itsadhesion to the supporting sheet, said coating differing in color fromthe color of the surface coated and so constituted that the impact ofmechanical force on said coating renders the coating translucent in theimpacted area. A schematic representation of the present novel recordingmedium is illustrated in FIGURE 1.

The polymeric substance to be used for producing the coating, accordingto the invention, are preferably polyolefins. Best results were obtainedwith polyethylene having a molecular Weight in the range of betweenabout 3000 and 150,000. According to a preferred embodiment of theinvention there is used a supporting sheet having a colored surface, thecolor of which determines the color of the resulting script or marks. Onthe other hand a colored coating may be resorted to. Although differentorganic binders may be used, especially satisfactory results wereobtained with natural or synthetic rubber or with polystyrene.

Recording media according to the invention may be used for differentpurposes. The use in automatic recording instruments is self evident, sois the use of suitably coated thin colored paper for obtaining copies oftype- Written script. taining copies of receipts and the like, writtenby a ball pen or the like.

It is clear that the thickness of the coating and its sensitivity haveto be adapted to the intended use. It is clear that a more sensitivecoating has to be used if the recording medium is to be used in asensitive and delicate scientific recorder than if same has to be usedfor copies of typewritten script. It has been found that coatings,having a thickness of between 5 and microns, give satisfactory results.

The coating is prepared from a solution obtained by dissolving apolymeric substance, such as polyethylene, in a suitable solvent, suchas aromatic hydrocarbons, aliphatic hydrocarbons or halogenatedhydrocarbons, if necessary at elevated temperatures, to which there isadded a suiiicient quantity of organic binder, such as natural orsynthetic rubber, polystyrene or the like. This coating is applied tothe supporting sheeting by any convenient means, such as brushing,coating or spraying, to result in an even layer of desired thickness.The coating solution contains between about 1% and 10% by weight of thepolymeric substance and from about 0.2% to 5% by weight of the organicbinder. Although the concentration of the polymeric substance and binderin the solvent has to be adjusted to the intended mode of application,it has been found that generally a 1 to 5% solution of the polymericsubstance (by weight) gave satisfactory results. A schematicrepresentation of the process steps for the preparation of the presentarticle is illustrated in FIGURE 2.

The invention is illustrated but not restricted by the followingexamples:

A sheet of paper having a blue glossy surface is coated on its coloredside by means of a solution prepared as follows: 6 grams of polyethyleneof molecular weight of about 6000 are introduced into 100 cc. of xylene,heated to a temperature of 65-70 C. and kept at this temperature untilthe polymer is dissolved. To the hot solution there are added about 10cc. of 5% solution (by weight) of polystyrene in benzene.

The solution is applied (preferably while still hot) to the colored sideor" the paper, so as to result in an even layer of about 1050 microns.Applications by means of brushing or spraying gave equally satisfactoryresults. After evaporation of the solvent the paper is ready for use.

The thus prepared recording medium gave a clearly legible script whenused underneath the original in a typewriter.

The thus prepared recording medium gave a clearly legible script whenused underneath the original written upon with a ball pen.

The thus prepared recording medium gave a clearly visible mark when usedin an automatic recording instrument, and subjected to the applicationof pressure by means of a stylus.

Example 2 Paper identical with the one used in Example 1, was coated bybrushing with a coating as used in Example 1, to which there was added0.1% by Weight of an aniline dye of red color, soluble in xylene. Theresultant coating had a red color, the script a blue one.

Example 3 White cardboard having a smooth surface, was coated with acoating as used in Example 2. The markings obtained were a differentshade of red than the color of the coating, clearly visible to the eye.

Such coated paper may be used for ob- A sheet of paper having a blacksurface, is coated on the colored side by means of a solution preparedas follows:

A quantity of 3 grams of polypropylene (having a melt index of 1-9,determined by ASTM D1238-52T, and a specific gravity of 0.90-0.91, andcommercially available as Moplen polypropylene resin from MontecatiniChemical Company) was dissolved in 100 ml. of boiling carbontetrachloride. After dissolution of the polypropylene a quantity of 10ml. of a 10% by weight solution of polyisobutylene in high boilinggasoline was added at a temperature of 70 C.

The coating of the paper with the solution was effected at an elevatedtemperature. After evaporation of the solvent the paper was ready foruse.

The thus prepared recording medium gave a clearly visible script whenused underneath the original in a typewriter. A number of satisfactorycopies could thus be obtained.

The paper was stored for a number of months without deterioration.

Although we have described our invention with a certain degree ofparticularity, it is understood that the present disclosure has beenmade by way of example only and that numerous changes in the details ofthe formulations may be resorted to, without departing from the spiritand the scope of the invention, as claimed hereinafter.

We claim:

1. A process for the production of a pressure sensitive recording mediumof the auto-copy paper type, which comprises (a) dissolving a materialselected from the group consisting of polyethylene having a molecularweight in the range of from 3,000 to 150,000 and polypropylene having amelt index of 1-9 and a specific gravity of 0.90-0.91, in a solventselected from the group consisting of aromatic hydrocarbons, aliphatichydrocarbons and halogenated hydrocarbons;

(b) adding an organic binder selected from the group consisting ofnatural rubber, synthetic rubber and polystyrene thereto, the resultingsolution containing from 1% to 10% by weight of said material and from0.2% to 5% by weight of said organic binder;

(c) applying said solution at an elevated temperature to a supportingsheet; and

(d) permitting said solvent to evaporate to produce an opaque layeradhered to the supporting sheet by said organic binder, said layerhaving a thickness of from 5 to 100 microns, and possessing a colordistinct from that of said supporting sheet.

2. A process for the production of a pressure sensitive recordingmedium, which comprises (a) dissolving a material selected from thegroup consisting of polyethylene having a molecular weight in the rangeof from 3,000 to 150,000 and polypropylene having a melt index of 1-9and a specific gravity of 0.90-0.91 in xylene;

(b) adding a solution of an organic binder selected from the groupconsisting of natural rubber, synthetic rubber and polystyrene thereto,the resulting solution containing from 1% to 10% by Weight of saidmaterial and from 0.2% to 5% by weight of said organic binder;

(c) applying said solution at an elevated temperature to a supportingsheet; and

(d) permitting the xylene to evaporate to produce an opaque layeradhered to the supporting sheet by said organic binder, said layerhaving a thickness of from 5 to microns and possessing a color distinctfrom that of said supporting sheet.

3. A process for the production of a pressure sensitive recording mediumwhich comprises (a) dissolving a material selected from the groupconsisting of polyethylene having a molecular weight in the range offrom 3,000 to 150,000 and polypropylene having a melt index of 1-9 and aspecific gravity of 0.90-0.91, at an elevated temperature in xylene;

(b) dissolving polystyrene in benzene and adding the resulting solutionto the solution of said material in xylene, the combined mixturecontaining from 1% to 10% by weight of said material and from 0.2% to 5%by weight of polystyrene;

(c) applying said mixture at an elevated temperature to a supportingsheet; and

(d) permitting the benzene and xylene to evaporate to produce an opaquelayer adhered to the supporting sheet by said polystyrene, said layerhaving a thickness of from 5 to 100 microns and possessing a colordistinct from that of the supporting sheet.

4. A recording medium comprising a supporting sheet coated with anopaque pressure sensitive layer adapted to be rendered translucent in apredetermined area upon the impact of mechanical force in such area,said recording medium having been produced by the process as defined inclaim 1.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Hahn: I. and E. Chem., vol. 37, No. 6, pp. 526-533, June1945, 117-161 VHH.

Polyethylene, Renfrew and Morgan, Iliffe and Sons, London, pages 397 and398. (Copy in Group 160.)

1. A PROCESS FOR THE PRODUCTION OF A PRESSURE SENSITIVE RECORDING MEDIUMOF THE AUTO-COPY PAPER TYPE, WHICH COMPRISES (A) DISSOLVING A MATERIALSELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE HAVING A MOLECULARWEIGHT IN THE RANGE OF FROM 3,000 TO 150,000 AND POLYPROPYLENE HAVING AMELT INDEX OF 1-9 AND A SPECIFIC GRAVITY OF 0.90-0.91, IN A SOLVENTSELECTED FROM THE GROUP CONSISTING OF AROMATIC HYDROCARBONS, ALIPHATICHYDROCARBONS AND HALOGENATED HYDROCARBONS; (B) ADDING AN ORGANIC BINDERSELECTED FROM THE GROUP CONSISTING OF NATURAL RUBBER, SYNTHETIC RUBBERAND POLYSTYRENE THERETO, THE RESULTING SOLUTION CONTAINING FROM 1% TO10% BY WEIGHT OF SAID MATERIAL AND FROM 0.2% TO 5% BY WEIGHT OF SAIDORGANIC BINDER; (C) APPLYING SAID SOLUTION AT AN ELEVATED TEMPERATURE TOA SUPPORTING SHEET; AND (D) PERMITTING SAID SOLVENT TO EVAPORATE TOPRODUCE AN OPAQUE LAYER ADHERED TO THE SUPPORTING SHEET BY SAID ORGANICBINDER, SAID LAYER HAVING A THICKNESS OF FROM 5 TO 100 MICRONS, ANDPOSSESSING A COLOR DISTINCT FROM THAT OF SAID SUPPORTING SHEET.